netdev - Re: Maximum MPLS labels on Linux network stack

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Date:   Wed, 3 May 2017 14:46:50 -0700
From:   Joe Stringer <joe@....org>
To:     Алексей Болдырев 
        <devel-net-ne-vlezay80@...dex.ru>
Cc:     David Ahern <dsahern@...il.com>, netdev <netdev@...r.kernel.org>
Subject: Re: Maximum MPLS labels on Linux network stack

On 3 May 2017 at 14:29, Алексей Болдырев
<devel-net-ne-vlezay80@...dex.ru> wrote:
> As I understand it, it's enough to just set the variable in the source
> #define FLOW_MAX_MPLS_LABELS 3
> on
> #define FLOW_MAX_MPLS_LABELS 7
> Or is there somehow still pitfalls?

You'll probably need to update the BUILD_ASSERT_DECL for the offset of
igmp_group_ip4, and for extra safety increment FLOW_WC_SEQ and inspect
each other place that has BUILD_ASSERT_DECL statements relying on that
FLOW_WC_SEQ. Changing FLOW_WC_SEQ will introduce compiler
warnings/failures so you can step through each location, take a look
if it's relevant and update the BUILD_ASSERT_DECL.

At a glance it seems like even with that bump, OVS userspace is only
detecting support for 3 labels so you might need to update something
kernel-side as well.